Test 1
Dr Lai grew some laboratory grown Staphylococci similar to the strains that were infecting
Harry in 3 different test tubes. These are known as controls.
 Test tube 1 – The bacteria with growth media alone
 Test tube 2 – The bacteria with antibiotics known to inhibit the growth of that bacteria
 Test tube 3 – Bacteria known to be resistant to the recommended antibiotics
Number of Bacteria
Number of Bacteria
Number of Bacteria
Results
Hours
Hours
Hours
Figure 1. No antibiotic.
Figure 2. Antibiotics
and sensitive bacteria.
Figure 3. Antibiotics with
sensitive and resistant
bacteria.
The growth of bacteria if NO
antibiotics are used.
The growth of bacteria with
active antibiotics.
The growth of resistant bacteria in
the presence of antibiotics
Conclusions
1. Why would Dr Lai find it necessary to carry out these control tests?
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2. What happens to the bacteria in each of the diagrams?
a. ___________________________________________________________
b. ___________________________________________________________
c. ___________________________________________________________
3. What happens to the bacteria in figure 3?
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4. Can you explain why this is happening?
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